Tail pulling means are already known in a plurality of different embodiments, as will be apparent inter alia from the U.S. Pat. Nos. 3,643,343, 3,277,550, 3,265,267 and 3,199,219. It is clear from these publications, especially the first-mentioned one, that in pulling the tail of a web-like material through a drying plant two different driving systems have to be utilized, one for the web-like material and one for the endless traction member in the form of a rope or belt. The reason for this is that the web-like material is subjected to longitudinal shrinkage during its advance through the dryer, due to drying, a velocity difference thus occurring between the web-like material and the traction member. When the tail is advanced through a dryer having considerable length, this velocity difference can cause a break in the web-like material, and for this reason special drive rolls and drive means for the tail puller must be installed in such dryers, and arrangements must be made to ensure that the velocities of the traction member and the web-like material do not deviate too much from each other, but keep within certain given limiting values which are dependent on the special conditions prevailing for the plant in question. These conditions are such as the length of the web-like material inside the dryer, the drying temperature, the moisture content of the material, its composition and its velocity in the dryer, which in other words is the time a certain section of the material is in the dryer. As a result of all the different conditions, there will be a difference between the peripheral velocity of the reversing rolls and the velocity of the web-like material through the dryer, since the conditions result in longitudinal dimensional alteration of the material, and this means that the traction member velocity must be adjusted to the actual velocity of the material in order that the velocity relationship between web and member will be kept within permitted values.
It will be clear from what has been said above that in the prior art a driving system for tail pulling is extremely complicated and thereby expensive, since complicated control equipment is required for driving the puller. Furthermore, special driving means are required for the puller, signifying in practice that it is impossible to install tail pulling equipment in an older type of existing dryer where there is no such modern facility.